In a self-winding watch, the wearer's movements are transmitted to the mainspring via an oscillating weight and a self-winding mechanism comprising a reduction gear.
The gear train of a self-winding mechanism is formed of toothed elements which transmit the force from the oscillating weight to the ratchet and enable the mainspring(s) to be wound. Upstream of the ratchet, this self-winding mechanism train usually includes, on the one hand, an intermediate train formed of an oscillating weight pinion and intermediate direction reverser wheel sets, and on the other hand, a reduction gear, arranged for reducing the initial velocity of the oscillating weight and increasing the force used for winding the mainspring.
Multiplying the complications in a mechanical watch leads, on the one hand, to complexity of the mechanisms of the movement, and on the other hand, to difficulty as regards the display, which is restricted by the available visible space on the front and possibly the back of the watch, or on additional surfaces such as the edges of the case or other surfaces. This problem is particularly acute when the watch is of small size, especially in the case of a ladies' or child's watch. Indeed, there is less available volume and the displays must remain legible, which requires maximising all the surfaces of the watch visible to the user.
The display of the power reserve on the oscillating weight is described in CH Patent No. 301 497, which discloses a self-winding watch including an oscillating weight whose motions are transmitted to a mainspring of the watch, said watch also including a power reserve indicator device including power reserve display means. There is also known from EP Patent No. 1 826 633 a self-winding watch including an oscillating weight whose motions are transmitted to a mainspring of the watch, said watch also including a power reserve indicator device comprising a power reserve display means, which is mounted on the oscillating weight. EP Patent Application No 2 360 535 A1 in the name of BLANCPAIN SA discloses a watch of this type, whose power reserve display and reference dial pivot synchronously at a given time.